Yes, but can a designer who sells designs for home builders use it in his designs?

If you sell a design with a similar recessed cockpit you will be infringing on a legitimate and legal US Patent. The Patent Holder can sue you.

In March 2013, I was contacted by a lawyer representing the Patent Holder informing me he felt there was an infringement on US Patent 6,779,477 and asked me to resolve the issue or they were prepared to seek recourse in court.

I discussed the numerous and various examples of prior art that would invalidate the patent with the Patent Holder, and eventually he stopped bothering me. I have not heard any more for over a year. It would appear to me that the Patent Holder has stopped defending his patent.

I would be happy to share my research into prior art with anyone who is interested.

It cost me time, but no money to make the threats of litigation stop.

TLDR: Yes, you can use the design and sell it. - but I'm not a lawyer.

Below is a "Blazing Aspens" design published in Sea Kayaker Magazine October 1999 that shows a recess almost identical to the patent claim